Abstract

An inadequate folate status is associated with increased risk of anaemia and neural tube defects. In many countries a folate intake below recommendations has been reported for women in childbearing age. However, data on folate intake and status are not always associated, since factors other than intake, e.g. bioavailability, affect folate status. This thesis studied the bioavailability of folate using in vivo and in vitro models. The effect of two pieces of Swedish nutritional advice on folate status of healthy women was assessed in a 12-week randomised controlled intervention trial. By combining a human plasma area under the curve (AUC)/ileostomy model with a stable isotope technique, the bioavailability of wholemeal bread fortified with reduced folate (5-CH3-H4folate) or folic acid was determined. In vitro effects of the food matrix on bioaccessibility and uptake of reduced folates were studied using a dynamic gastrointestinal model (TIM) and Caco-2 cells. The intervention breakfast diet (contributing ~1/3 of recommended daily folate intake) significantly improved folate status of the women, indicating a high folate bioavailability. The bread intervention diet (contributing ~1/5 of recommended daily folate intake) maintained folate and decreased homocysteine concentrations. Based on folate content in stomal effluent, the bioavailability of both folate fortificants tested was similarly high (~90%) but plasma kinetics differed significantly depending on ingested folate form. Data from in vitro TIM and Caco-2 cell experiments showed an inhibitory effect (~25%) of the bread matrix on bioaccessibility and uptake of reduced folates, which was higher than in vivo findings. Overall, data from these in vivo and in vitro studies suggest that the bioavailability of reduced folate is high and comparable to that of synthetic folic acid. Food matrix effects, e.g. of bread or a typical breakfast meal, on folate bioavailability seem negligible at physiological folate intake doses.